JPH0617591B2 - Running hydraulic circuit of hydraulic shovel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a traveling hydraulic circuit of a hydraulic shovel having a counterbalance valve.

<Prior Art> FIG. 4 is a circuit diagram showing a traveling hydraulic circuit of a conventional hydraulic shovel of this type. In this figure, 1 is a hydraulic pump,
Reference numeral 2 is a traveling motor of the hydraulic shovel, 3 is a control valve for controlling the drive of the traveling motor 2, and 4 is a relief valve that regulates the maximum pressure of the hydraulic circuit. Reference numerals 5 and 6 denote cross relief valves provided between the pipelines 16a and 16b on both sides of the traveling motor 2 so that the oil in the pipelines flows from the high pressure side to the low pressure side. 7 is a counterbalance valve, which is a conduit 15 from the control valve 3.
It is installed between a and 15b and the pipelines 16a and 16b of the traveling motor 2. Reference numeral 8 denotes a counter balance valve spool which can be switched between a neutral position and a left and right position. 9a,
9b is a pilot chamber provided on both sides of the spool 8, 10a and 10b are inlet ports of the counterbalance valve 7, and 11a and 11b are outlet ports. 12a, 12
b is the pilot chamber 9a, 9b and the inlet port 10a, 10
throttles 13a and 13b provided between the inlet ports 10a and 10b and the outlet ports 11a and 11b.
It is a check valve provided between and.

When the control valve 3 is switched to, for example, the left position in order to drive the hydraulic shovel, the pressure oil of the hydraulic pump 1 is supplied to the traveling motor 2 via the pipe line 15a, the check valve 13a and the pipe line 16a. At this time, the pressure in the pipe line 15a rises, and this pressure is transmitted to the pilot chamber 9a via the throttle 12a, so that the spool 8 moves to the right and is switched to the left position. The pressure oil supplied to the traveling motor 2 includes a pipe line 16b, an outlet port 11b, the spool 8 that has been switched, an inlet port 10b, a pipe line 15b, and a control valve 3.
It is returned to the tank through. Thereby, the traveling motor 2
Is driven, and the hydraulic shovel travels in the direction corresponding to the switching of the control valve 3.

In this state, when the road goes downhill and the hydraulic shovel starts to run downhill, the traveling motor 2 pumps. For this reason, the pressure in the conduit 16a decreases, and the conduit 16b
And the spool 8 of the counterbalance valve 7 moves to the left by an amount corresponding to the pressure drop in the pipelines 16a and 15a, and narrows the return passage from the pipeline 16b to the tank. As a result, the pressure in the conduit 16b further increases and acts as a brake on the travel motor 2, and when the pressure in the conduit 16b reaches a set value, the cross relief valve 5 opens and the conduit 16
The oil of b is made to flow into the pipeline 16a, and the inertia energy of the traveling motor 2 is absorbed.

If the throttle 12a is not provided during traveling on such a downhill, the pressure in the pipe line 15a is immediately transmitted to the pilot chamber 9a, and the spool 8 is constantly moved to the left and right in accordance with the change in the pressure in the pipe line 15a. It oscillates to cause oscillation and cannot be stopped at the proper position. Aperture 12a (1
2b) is provided for this purpose, the spool 8
The above oscillation is prevented by applying damping to the. In this way, the throttle 12a (12b) effectively exhibits its function when traveling downhill, but during other operations of the hydraulic shovel, the throttle 12a (12b) gives excessive damping to the spool 8 and extremely Inconvenient situations may occur. An example of such a case will be described below.

In the case of a hydraulic shovel, a sudden reverse operation may be performed during traveling from forward to reverse or from reverse to forward. Also, if mud, pebbles, etc. adhere to the tracks, put a bucket on the ground to drop the mud, pebbles, etc., and tilt the hydraulic shovel between the front and one of the tracks to support it. There are cases where work is performed to drive the crawler belt in the normal and reverse directions. In order to perform these operations, first, as described above, the control valve 3 is switched to the left position and the traveling motor 2 is moved.
Is driven in one direction, and then the control valve 3 in the left position is switched to the right position in order to reverse the traveling motor 2. Then, the supply of the pressure oil to the pipe 15a is cut off and the pressure is reduced, and this is transmitted to the pilot chamber 9a via the throttle 12a. Therefore, the spool 8, which has reached the stroke end in the right direction, returns to the neutral direction and enters the inlet ports 10a, 10b and the outlet ports 11a, 11.
Close the circuit with b. As a result, the traveling motor 2 performs a pumping action due to its inertia, and the discharge side conduit 1
The pressure of 6b is increased and the traveling motor 2 is braked. The inertia energy of the traveling motor 2 is the cross relief valve 5
The oil is absorbed by the circulation of oil from the conduit 16b to the conduit 16a. On the other hand, when the control valve 3 is switched to the right position, the pressure in the pipe line 15b becomes high, and the pilot chamber 9
The pressure of b also rises. When the absorption of the inertial energy of the traveling motor 2 is finished and the pressure at the outlet port 11b decreases and the pressure at the inlet port 10b becomes higher, the pressure oil of the hydraulic pump 1 becomes the control valve 3, the pipe line 15b, and the check. It is supplied to the traveling motor 2 through the valve 13b and the conduit 16b,
Reverse the traveling motor 2. During this period, the spool 8 is positively moved to the left due to the pressure increase in the pilot chamber 9b as described above.

<Problems to be Solved by the Invention> However, in the above-described conventional traveling hydraulic circuit, when the spool 8 is moved to the left, the oil in the pilot chamber 9a is brought into the inlet port by the pressure in the pilot chamber 9b. 1
The discharge flow rate of oil is greatly resisted by the presence of the throttle 12a, the pressure in the pilot chamber 9a rises to almost the same pressure as the pressure in the pilot chamber 9b, and eventually, The shift of the spool 8 to the left is a constant speed movement. On the other hand, in the case of idling of the crawler belt or rapid switching between forward and backward movements, the reverse rotation of the traveling motor 2 is performed within a short time after the control valve 3 is switched to the right position. This time is shorter than the time for which the spool 8 is switched to the right position while receiving the resistance of the diaphragm 12a. Therefore, when the traveling motor 2 reversely rotates, the outlet port 11a and the inlet port 10a are closed, and the pressure in the pipeline 16a becomes almost equal to the pressure in the pipeline 16a due to the reverse rotation of the traveling motor 2. Further, a pressure higher by the amount of inertial force absorption of the traveling motor 2 in the reverse direction is trapped in the conduit 16a. In this case, the cross relief valves 5 and 6 are normally connected to the conduit 16a,
Since it operates by the differential pressure between 16b, the relief operating pressure of the conduit 16a when the high pressure (supply pressure from the hydraulic pump 1) acts on the conduit 16b as described above,
The sum of the pressure of b and the set pressure of the cross relief valve 6 results in an extremely high closing pressure.

As described above, when the diaphragm 12a is present, the spool 8
If the inertial force of the traveling motor 2 is low and the speed is reversed, there is a risk that abnormally high pressure will occur in the discharge side pipe line 16a of the traveling motor 2 and the life of the traveling motor 2 will increase. Have an adverse effect. The occurrence of such an abnormally high pressure may occur not only in the forward / backward idle operation of the crawler belt or in the abrupt forward / backward operation, but also in other operations.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to provide a traveling hydraulic circuit of a hydraulic shovel capable of preventing generation of undesired closing pressure in a traveling motor and a counterbalance valve. To provide.

<Means for Solving Problems> In order to achieve this object, the present invention provides a traveling motor,
A control valve that controls the drive of the traveling motor, a hydraulic pump that supplies pressure oil for driving to the traveling motor via the control valve, and a control valve that is provided between the traveling motor and the control valve 1st where circuit pressure is led
And a second pilot chamber, and a counterbalance valve having a spool operated by pressure oil in both of these pilot chambers, in which the spool of the above-mentioned counterbalance valve is divided into two parts so that they face each other. The third pilot chamber formed in the above and the high pressure side of the main circuit pressure described above are provided, and a pressure selecting means for supplying the pressure as the pilot pressure to the third pilot chamber is provided, and the control valve is an open center spool. And a motor port and a tank port, which communicate with each other through a throttle when neutral.

<Operation> In the traveling hydraulic circuit of the hydraulic shovel of the present invention, as described above, the spool of the counterbalance valve is divided into two, and the third pilot chamber is provided between these spools. When the reverse rotation drive of the motor is started, that is, when the control valve is switched, the discharge oil of the hydraulic pump becomes the third
Of the counterbalance valve on the side to which the discharge oil of the traveling motor is guided is instantaneously switched, and the spool on the side to which the discharge oil of the traveling motor is guided is instantaneously switched. Since the port and the inlet port are electrically connected, it is possible to prevent the generation of an undesired trapping pressure of the discharge oil of the traveling motor.

In addition, since the control valve is set to the open center as described above and the motor port and the tank port are communicated with each other through the throttle at the neutral position, the control valve is set to the neutral position when the traveling motor is stopped. When the valve is returned to the control valve, a brake pressure for stopping the traveling motor can be generated by the throttle, that is, both the control valve and the counter balance valve can generate the brake pressure, and the control can be performed. The brake pressure by the valve can be generated before the brake pressure is generated by the counter balance valve, and thus the brake pressure generation time can be secured for that long, and the shock when the travel motor is stopped can be alleviated.

<Example> Hereinafter, a traveling hydraulic circuit of the hydraulic shovel of the present invention will be described with reference to the drawings.

1 to 3 are explanatory views showing an embodiment of the present invention, FIG. 1 is an overall circuit diagram, FIG. 2 is an enlarged view showing a control valve, and FIG. 3 is shown in FIG. It is a characteristic view which shows the position A of the spool of a control valve, and the relationship of opening area B.

In FIG. 1, reference numerals 8a and 8b denote spools of the counter balance valve 7, which can be switched to left and right positions. Two
Reference numeral 0 is a third pilot chamber provided facing the opposite ends of both spools 8a and 8b, and 21 is both inlet ports 10a, 10
A shuttle valve provided between b and 22 is a throttle provided between the shuttle valve 21 and the third pilot chamber 20, and the shuttle valve 21 includes both inlet ports 10a, 10a and 10b.
One of the high pressure side b is selected and the pressure is transmitted to the third pilot chamber 20 via the throttle 22.

Reference numeral 30 is a control valve for controlling the drive of the traveling motor 2, which has an open center spool and which, as shown in FIG.
The outlet port 30d, the inlet / outlet port 30f, and the tank port, that is, the outlet port 30c are throttled 25a, 25
It is set to communicate via b.

The operation of the embodiment thus configured will be described below.

When the control valve 30 is switched to the left position, the pressure oil of the hydraulic pump 1 flows through the conduit 15a, the check valve 13a, and the conduit 16a.
It is supplied to the traveling motor 2 via a. At this time, the shuttle valve 21 selects the pressure oil on the high pressure side inlet port 10a side from both the inlet ports 10a and 10b.
The pressure oil of 0a is introduced into the third pilot chamber 20 via the shuttle valve 21 and the throttle 22, and the pressure oil of the inlet port 10a is also introduced into the pilot chamber 9a via the throttle 12a, and eventually the spool 8a. Does not move because it receives the same pressure from opposite directions. On the other hand, the pilot chamber 9b has a diaphragm 12b.
Communicates with the low pressure inlet port 10b via the
When the pressure in the pilot chamber 20 rises above the pressure to overcome the force of the spring 24b, that is, the cracking pressure or more,
The spool 8b is pressed to the right by the pressure oil in the third pilot chamber 20, so that the outlet port 11b and the inlet port 10b are electrically connected. That is, the traveling motor 2
The pressure oil discharged from the pipe 16b, the outlet port 11b,
Return to the tank through the inlet port 10b, the line 15b and the control valve 30.

Here, the operation of the control valve 30 among the above operations will be described in detail with reference to FIGS. 2 and 3. In addition,
In FIG. 2, A ₀ indicates a neutral position, A ₄ indicates a left side position, and A ₀ , A _{4 in} the spool position A in FIG.
2 are positions shown in FIG. 2, A ₁ , A ₂ , and A ₃ are spool positions between the neutral position A ₀ and the left position A ₄ , B ₀ is the minimum opening area, and B ₁ is the maximum opening area. Is shown. Further, in FIG. 3, C is port 30c and port 30d.
Shows the characteristic line of the opening area of the communication passage of D, and D is the port 30b
And the characteristic line of the opening area of the communication passage of the port 30e,
Shows a characteristic line of the opening area of the communication passage of the ports 30a and 30d, and F shows a characteristic line of the opening area of the communication passage of the ports 30c and 30f.

Then, the control valve 30 is set to the neutral position A as described above.
_When switching from ₀ to the left side position A ₄ , the process from the start to the end of switching is seen in the characteristic diagram of FIG. 3, and as the spool moves in the direction from position A ₀ to position A ₄ , the port 3
0c and the port 30d are closed at the position A ₁ as indicated by the characteristic line C representing the communication state. Then, the spool starts to open from the position A ₂ as shown by the characteristic line representing the communication state of the ports 30a and 30d. As a result, the oil discharged from the hydraulic pump 1 begins to be supplied to the conduit 15a shown in FIG.
Further, as indicated by the characteristic line D representing the communication state between the ports 30b and 30e, the communication passage between the ports 30b and 30e is wide open at the position A ₀ , and accordingly, the hydraulic pump 1 and the tank are communicated with each other. The oil discharged from the hydraulic pump 1 was escaped to the tank. Here, when the spool moves to the vicinity of the position A _{2, the} area of the communication passage between the port 30b and the port 30e decreases as shown by the characteristic line D, that is, the communication passage is narrowed. As a result, pressure is generated in the discharge pipe line of the hydraulic pump 1, and the pressure oil flows into the pipe line 15 a communicating with the traveling motor 2.

Further, as indicated by a characteristic line F representing the communication state between the ports 30f and 30c, F is present in the vicinity of the position A ₀ to the position A _2.
1 , the port 30f and the port 30c communicate with each other through the diaphragm 25b shown in FIG.
The area of the throttle 25b portion starts to expand after passing ₂ and the communication passages of the ports 30f and 30c are completely opened near the positions A ₃ and A ₄ . As a result, as described above, the conduit 15b communicates with the tank, and the traveling motor 2 operates. Further, the communication passage between the port 30b and the port 30e is also completely closed at the position A _{3 as} shown by the characteristic line D, whereby all the pressure oil of the hydraulic pump 1 is sent to the traveling motor 2 through the pipe line 15a.

Further, in this embodiment, for example, when the traveling motor 2 is driven as described above and the hydraulic shovel is traveling, when the road becomes a downhill and the hydraulic shovel starts traveling on this downhill, The traveling motor 2 acts as a pump. For this reason, the pressure in the conduit 16a decreases, and the conduit 16b
And the spool 8b moves to the left by an amount corresponding to the pressure decrease in the third pilot chamber 20, which changes in accordance with the pressure decrease in the pipes 16a and 15a, and returns to the tank from the pipe 16b. Is squeezed and the vehicle travels with the hydraulic brake applied.

In this way, when there is a load change such as a change in the road surface condition on a slope, the throttles 12b and 22 supply the pressure oil to the pilot chambers 9b and 20 at both ends of the spool 8b, and the throttle 1b.
2a and 22 are pilot chambers 9a at both ends of the spool 8a,
Resistance is applied to the supply and discharge of the pressure oil to and from 20 to prevent the spools 8a and 8b from oscillating.

Further, in this embodiment, when the control valve 30 located at the left side position A ₄ is switched to the right side position A ₅ while running or when the track is idling, the discharge oil of the hydraulic pump 1 is supplied to the pipeline by the control valve 30. The oil passage is switched from 15a to the pipe 15b, pressure oil is supplied to this pipe 15b, and the shuttle valve 21 selects the inlet port 10b on the high pressure side from both inlet ports 10a and 10b, and the pressure of the inlet port 10b is selected. The oil is transmitted to the third pilot chamber 20 via the shuttle valve 21 and the throttle 22. Also, the pressure oil of the inlet port 10b is similarly guided to the pilot chamber 9b through the throttle 12b, so that the pressures of the pilot chambers 9b and 20 at both ends of the spool 8b become the same pressure, and the spool 8b exerts the force of the spring 24b. Continue to recover with only. On the other hand, the pressure in the conduit 15b rises,
When the pressure in the third pilot chamber 20 reaches or exceeds the cracking pressure of the spring 24a, the spool 8a is pressed to the left by the pressure oil in the third pilot chamber 20, and the connection between the outlet port 11a and the inlet port 10a is established. To do.

When the pressure in the pipe 15b further rises and becomes higher than that in the pipe 16b, the check valve 13b is opened, and the pressure oil of the hydraulic pump 1 is supplied to the traveling motor 2 via the pipe 15b, the check valve 13b, and the pipe 16b. Then, the traveling motor 2 is rotated in the reverse direction.
When the reverse rotation drive of the traveling motor 2 is started, the discharge port 11a and the inlet port 10a are already in the conductive state as described above.
There is no possibility that abnormal high pressure will be generated in the conduit 16a by returning to the tank without being confined in the. Since the operation from reverse rotation to normal rotation is performed in the same manner, its explanation is omitted.

Further, in this embodiment, when the control valve 30 located at the left side position A ₄ in FIG. 2 is switched to the neutral position A ₀ in order to stop the driving of the traveling motor 2, each control valve 30 is controlled. The communication passage changes its opening area from the position A ₄ shown in FIG. 3 to the position A ₀ . First, as indicated by the characteristic line F representing the communication path between the ports 30f and 30c, the communication path was opened at the maximum at position A ₄ , but the opening was caused by the movement toward the position A _0. The area is gradually reduced, and as a result, brake pressure is generated in the conduit 15b shown in FIG.

Then, this brake pressure is applied from the pipe line 10b to the shuttle valve 2
1 through the diaphragm 22 and the third pilot chamber 20
Be led to. On the other hand, it is also guided from the pipe line 10b to the pilot chamber 9b through the diaphragm 12b. Therefore, the pressures of the pilot chambers 9b and 20 at both ends of the spool 8b become equal, and the spool 8b moves toward the neutral position A ₀ only by the force of the spring 24b. At this time, the moving speed of the spool 8b is determined by the flow rate of the oil sucking and discharging the throttles 22 and 12b. When the spool 8b starts moving to the neutral position A ₀ , a brake pressure is generated in the pipe 16b by narrowing the return passage from the pipe 16b to the tank. That is, the braking force acting on the traveling motor 2 is reduced by squeezing the return passage from the conduit 15b to the tank by moving the spool of the control valve 30 in the neutral direction.
There are two stages: a brake pressure transmitted from the pipe 15b and generated in the pipe 16b, and a brake pressure generated by the spool 8b of the counterbalance valve 7 moving in the neutral direction. Therefore, if the throttles 25b of the spool of the control valve 30 and the throttles 22 and 12b of the pilot chambers 20 and 9b at both ends of the spool 8b of the counterbalance valve 7 are selected to the optimum conditions, the two-stage brake pressure can be obtained. Therefore, it is possible to suppress the shock when the traveling motor 2 is stopped.

Further, the spool of the control valve 30 is located at the position A in FIG.
_While moving from ₃ to the position A ₂ , the hydraulic pump 1 still sends the pressure oil to the pipe line 15a because the communication passage between the port 30b and the port 30e is narrowed as shown by the characteristic line D. Therefore, the pressure is transmitted to the shuttle valve 21. From this fact, when the brake pressure actually generated in the pipe line 15b becomes higher than the pump pressure generated in the pipe line 15a, the spool 8b of the counter balance valve 7 starts to move in the neutral direction. . That is, the timing at which the brake pressure generated by the spool of the control valve 30 rises and the timing at which the brake pressure generated by the spool 8b of the counterbalance valve 7 rises are deviated, which causes the traveling motor 2 to stop. The braking pressure to be generated can be generated for a long time, and from the viewpoint different from the above, it is possible to suppress the shock when the traveling motor 2 is stopped.

The operation of stopping the drive of the traveling motor 2 as described above is similarly performed when the control valve 30 is switched from the right side position A _{5 in} FIG. 2 to the neutral position A ₀ .

In the embodiment thus configured, even when one spool of the counter balance valve 7 is in the process of returning to the neutral direction during the reverse rotation operation of the traveling motor 2, the other spool of the counter balance valve 7 rises in the reverse rotation drive pressure. Since the cracking is performed on the way, it is possible to prevent the high confining pressure from being generated in the pipe lines 16a and 16b between the traveling motor 2 and the counter balance valve 7. The effect is, for example, a sudden reverse rotation operation of the control valve 30 in which the reverse rotation pressure rise timing of the pipe 15b is earlier than the neutral return of the spool 8b, or a track idle rotation in which the rapid reverse rotation timing of the traveling motor 2 is earlier. Remarkably appears.

Further, in this embodiment, as described above, when the traveling motor 2 is stopped, two levels of brake pressure, that is, the brake pressure by the spool of the control valve 30 and the brake pressure by the spool of the counter balance valve 7, can be obtained, and Since the timings at which these brake pressures are generated are deviated, it is possible to suppress shocks when the traveling motor 2 is stopped.

Further, in this embodiment, meter-out control can be performed, and metering during deceleration can be expanded.

Further, in this embodiment, when the traveling motor 2 is stopped, the spool of the control valve 30 is first braked, and therefore, even if the spool of the counterbalance valve 7 is slowly returned to the neutral position, no cavitation occurs.

Although the shuttle valve 21 is described as an example of the pressure selecting means in the above-described embodiment, a structure in which a check valve is combined may be used instead of the shuttle valve 21.

<Effects of the Invention> Since the traveling hydraulic circuit of the hydraulic shovel of the present invention is configured as described above, it is possible to prevent an undesired confining pressure from being generated in the conduit between the counter balance valve and the traveling motor. Can be prevented. Further, since the brake pressures generated by both the control valve and the counter balance valve can be generated at different timings, it is possible to suppress the shock when the traveling motor is stopped.

[Brief description of drawings]

1 to 3 are explanatory views showing an embodiment of a traveling hydraulic circuit of a hydraulic shovel according to the present invention. FIG. 1 is an overall circuit diagram, FIG. 2 is an enlarged view showing a control valve, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the position A of the spool of the control valve shown in FIG. 2 and the opening area B, and FIG. 4 is a circuit diagram showing a traveling hydraulic circuit of a conventional hydraulic shovel. 1 ... hydraulic pump, 2 ... travel motor, 7 ... counter balance valve, 8a, 8b ... spool, 9a, 9b ...
Pilot room, 10a, 10b ... Entrance port, 11
a, 11b ... Exit port, 12a, 12b, 22, 2
5a, 25b ... Throttle, 13a, 13b ... Check valve, 16a, 16b ... Pipe line, 20 ... Third pilot chamber, 21 ... Shuttle valve (pressure selection means), 24a,
24b ... spring, 30 ... control valve.

Claims (1)

[Claims] 1. A traveling motor, a control valve for controlling driving of the traveling motor, a hydraulic pump for supplying pressure oil for driving to the traveling motor via the control valve, the traveling motor and the control valve. A traveling hydraulic circuit of a hydraulic shovel, which is provided between the first and second pilot chambers, through which a main circuit pressure is introduced via a throttle, and a counter balance valve having a spool operated by pressure oil in both pilot chambers. In the above, the spool of the counterbalance valve is divided into two, a third pilot chamber formed so as to face both spools and a high pressure side of the main circuit pressure are selected, and the pressure is used as the pilot pressure. 3 is provided with a pressure selecting means for supplying to the pilot chamber, and the control valve is an open center spool and a neutral valve. Travel hydraulic circuit of the hydraulic Shiyoberu characterized by having a motor port and the tank port communicate with each other through the aperture.